third_party/libvpx/source/libvpx/examples/force_keyframe.txt

@TEMPLATE encoder_tmpl.c
Forcing A Keyframe
==================
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION
This is an example demonstrating how to control placement of keyframes
on a frame-by-frame basis.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ INTRODUCTION


Configuration
-------------
Keyframes can be forced by setting the VPX_EFLAG_FORCE_KF bit of the
flags passed to `vpx_codec_control()`. In this example, we force a
keyframe every 8 frames.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  PER_FRAME_CFG
if(!(frame_cnt & 7))
    flags |= VPX_EFLAG_FORCE_KF;
else
    flags &= ~VPX_EFLAG_FORCE_KF;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PER_FRAME_CFG


Observing The Effects
---------------------
The output of the encoder examples shows a 'K' rather than a dot '.'
when the encoder generates a keyframe. Note that every 8 frames a 'K'
is output.